1. Field of the Invention
The present invention relates to an operation unit structured by unitizing a throttle operating lever of an engine and a start switch which can be applied to various working devices provided with an engine as a source of power and a self starter such as a trimmer, a chain saw, a rotation saw or the like, or a power spreader, various farm working machines or the like, and more particularly to an operation unit of an engine which eliminates an erroneous operation of the start switch based on a simple mechanism.
2. Description of the Related Art
An engine provided with a self-starter actuates a start motor by operating a start switch, and starts the engine based on the actuation. A rotation speed of the engine is controlled by operating a throttle lever so as to control an opening degree of a throttle valve via a control wire. When the rotation speed of the engine reaches a predetermined rotation speed, a clutch within a clutch housing engages so as to start an actuation of a rotary blade or the like. When stopping the rotation of the engine, an engine stop switch is turned on. In conventional, the start switch and the engine stop switch are independently provided, however, for example, according to a switch apparatus described in Japanese Utility Model Application Publication (JP-Y) No. 1-22194, a single movable contact having three contact points is provided, the contact is structured such that a pressure button rotating an operation knob and actuating a start switch provided within the operation knob is pressure actuated to a terminal side, an engine stop switch is changed between a stop position and a working position based on the rotating operation of the knob, and the start switch and the stop switch are composed such that an OFF state, that is, a stop state of the engine is maintained even if the pressure button is pushed at a time when the stop switch is at the stop position, and the engine is started by pushing the pressure button only when the stop switch is at the working position.
Further, for example, according to Japanese Utility Model Application Publication (JP-Y) No. 7-5233, an apparatus is structured by a throttle operating lever, a start and stop operating lever, one control wire in which one end is coupled to the throttle operating lever, and an interlocking mechanism controlling an opening degree of the throttle valve, an actuation of a start switch actuating a start motor and an actuation of an engine stop switch interlocking with a working state of the control wire. Further, a start safety lock lever is arranged near the throttle operating lever. The throttle operating lever, the start and stop operating lever and the start safety lock lever are arranged in a handy operating portion intensively.
In the engine control apparatus according to JP-Y No. 7-5233, the opening degree of the throttle valve of the engine is controlled from an idle position to a full-open position based on the operation of the throttle operating lever. The start and stop operating lever is at a reference position which can be freely operated by the throttle operating lever, is moved to a stop position locking to the start safety lock lever so as to stop the engine, and is moved further to a start position after releasing the lock by the start safety lock lever so as to start the engine. Further, the one control wire is actuated in correspondence to an operated state of the throttle operating lever and the start and stop operating lever, and the interlocking mechanism controls the opening degree of the throttle valve, the actuation of the start switch actuating the start motor and the actuation of the engine stop switch stopping the engine, interlocking with the working state of the control wire.
According to the engine control apparatus, when operating the throttle operating lever and the start and stop operating lever in accordance with a required procedure, the working state is transmitted to the interlocking mechanism via the one control wire, the opening degree of the throttle valve, the actuation of the start switch and the actuation of the engine stop switch are controlled by the interlocking mechanism in correspondence to the working state, and the engine is controlled to a desired start or stop state, or a desired rotation speed. Further, since the throttle operating lever and the start and stop operating lever are provided in the operating portion in the working machine, and the interlocking mechanism, the start switch and the engine stop switch are provided in the prime mover portion, it is possible to control all of the engine start and stop and the rotation speed by the handy portion. Accordingly, an operability is excellent, an electric wiring to the start switch and the engine stop switch can be simplified, and a connecting line connecting the operating portion and the prime mover portion can be constituted only of the one control wire so as to improve an outer appearance.
Meantime, the composite switch apparatus disclosed in JP-Y No. 1-22194 mentioned above is structured such that the start switch of the self-starter and the engine stop switch are integrally installed and composed, however, the start switch is turned on by pushing the start button, for example, unless the operating knob for the engine stop switch is rotated to the stop position, so that the engine rotation starts. Accordingly, it is required to make certain of the fact that the operating knob is not at the stop position every time when it is intended to start the engine. Further, according to JP-Y No. 1-22194 at this time, there is no description which directly associates the operation of the throttle operating lever operating so as to open and close the throttle valve of the engine with the composite switch apparatus as far as it is determined based on the drawings thereof. Accordingly, even if the throttle operating lever is in the operated state, the working device such as the rotary blade or the like is actuated by pushing the start button as mentioned above.
On the other hand, according to the engine control apparatus described in JP-Y No. 7-5233 mentioned above, there is no risk that the working device or the like is erroneously actuated as far as the throttle operating lever and the start and stop operating lever is not erroneously operated. However, its mechanism and operating procedures are extremely complicated and troublesome, an accuracy of parts is required, and it is troublesome to maintain the parts. Further, the erroneous operation tends to be generated in the throttle operating lever and the start and stop operating lever, it is hard to simply start and stop the engine itself, and a smooth operation is expected only by persons of experience in the art.